Several cytoarchitectonic areas can be distinguished along the cortex buried within he Sylvain fissure in primates and amongst these, cutaneous stimulation activates neurons in the second somatosensory area (SII), retroinsular cortex (Ri), granular insula (Ig) and a portion of area 7 (7b). The objectives for this project are 1) to determine the best tactile stimulus for neurons in these cortical loci by analyzing quantitatively responses to controlled mechanical stimuli including different frequencies of vibrotactile stimulation; 2) to examine neuronal activity to sinusoidal tactile stimulation when the probe tip size is changed, when rigid surrounds encircle the stimulation site, and when the receptive field is first exposed to conditioning mechanical stimulation of different frequencies; 3) to study the effects of conditioning electrical stimulation of SI on neuronal responses in SII; and 4) to record the neuronal responses in these regions in animals behaviorally conditioned to perceive various somatosensory stimuli under different expectancy conditions. These studies may further define the function of SII and the surrounding areas in somesthesis and may indicate why destruction of these areas in primates leads to alteration in attention to somesthetic stimuli.